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Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: PRZNBUS on December 02, 2015, 04:21:09 AM
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I was told by a knowledgeable electrical friend of mine you shouldn't use house style wires in a conversion. He said something about they need to be rated for movement? He said either automotive, boat or even extension cords with the ends cut off are better choices but way more expensive than house rated wire. I trust this guy and can sort of see what he's stating but how many people are using regular house stuff?
Bruce
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Most likely is the difference between house wire being solid core while auto/marine is stranded. More forgivability of movement and vibration resistance with stranded. Solid can crack over time.
Ryan.
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I used 12 gauge stranded THHN rated bought at Home Depot $50 for 500ft, pulled through light weight plastic conduit. Hence you have to use three wires for grounding. 12 gauge is rated at 20 amps at 120vac. And since no run in a bus is more than 40 ft, you'll be good-especially if your using 15 amp breakers. Good Luck, TomC
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This is a old debate Romex has always been used in the RV industry if anchored it will last seems like for ever.
I didn't use Romex I used the thinn marine wire and 10 years later I found out it wasn't recommend for RV use so who knows I wouldn't be afraid of using Romex .
I have a 30 year old Coachmen with it and a 1998 Trek wired with Romex fwiw never a problem with either and you don't need conduit for Romex it is double shielded.There is a section in the RVIA book on wiring fwiw
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I used 20 amp breakers on A/C, and 15 amp breakers on everything else. I wired my bus with 10 gauge-a bit over kill and harder to pull through conduit. I would use the conduit to measure my run then pull the wire through before installing. Good Luck, TomC
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Extensions cords are sometimes used (and apparently with some success) but the pro electricians consider them not up to the task for RV/bus conversion wiring. Since they're made to be light-duty and flexible versus vibration-resistant, I won't argue with that.
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Seems like I read some place that the problem with extension cords is they get hot easy. With three wires wrapped together, it is harder for heat to dissipate.
The extra benefit of the stranded wire is, it is so much easier to pull through tight spaces. It is easier to mount on a post and clamp down in a breaker. We have both and the stranded is so much easier.
Don and Cary
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Seems like I read some place that the problem with extension cords is they get hot easy. With three wires wrapped together, it is harder for heat to dissipate. ...
Yes, the light (for flexibility) construction is a factor in thin strands, easily broken by vibration or pulling. All the power goes through fewer and fewer strands at each wear/weak point until they melt down.
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Although there may be superior options, the one factory RV I had and the two buses were all done with Romex. This covers at least 30 years of experience and I have never had a problem with it. Also, I know some people are very critical of using stranded extension cord but I question whether much of the opposition to it is more theoretic than real. I am sure that some on this board have used at least some of it and wonder if they have ever had a problem. If I wanted to use the stuff and also wanted to be cautious, I would just go with a thicker gauge.
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I was told by a knowledgeable electrical friend of mine you shouldn't use house style wires in a conversion. He said something about they need to be rated for movement? He said either automotive, boat or even extension cords with the ends cut off are better choices but way more expensive than house rated wire. I trust this guy and can sort of see what he's stating but how many people are using regular house stuff?
Bruce
What would cause movement in the wiring?
Wes
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All the vibrations of the vehicle constantly moving. It adds up over time. I don't have the numbers but there have been quite enough rv fires started because of wiring failures to ward me from using solid wire romex. ALL vehicle manufactures use stranded wire in autos and trucks and factory bus wiring. It's possible some rv manufactures have used solid in their builds and I'm sure the majority of them have had no problems. But the ones who have are enough for me to not want that risk
FWIW
Eric
Sent from my XT1254 using Tapatalk
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I don't think you see many RV fires caused by Romex wiring on the AC side most fires start on the DC side at some component like on any RV including the Prevost conversions with stranded wire,any type wire will start a fire when overloaded for long periods JMO
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I used all aluminum metalic sheathed 12 guage copper for everyting, keeps the mice from chewing into the covering.
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Just a few tidbits re electrical:
1. Best wire =A/C stranded, more current, D/C solid for heat. Never use anything smaller than 12 gauge wire. You have to think about the heat load.
2. Don’t stretch the wire tight but secure it close to the termination points and so it doesn’t flop and move like a fish out of water.
3. Don’t make sharp turns, loop the wire.
4. Don’t make snug holes through dividers, keep it loose.
5. Distance and CURRENT, know what the device draws. Just because its 12 volts don’t mean you can use 12 gauge wires. If it’s drawing 30 amps and a 40 foot run with 10 bends, go to 10 gauge wires.
6. Termination points: use care making sure you strip enough but not too much insulation from the wire and never, I mean never use Home Depot 15 cent outlets and switches. Using the push in connector devices are ok in houses but we have vibration, use the screws with proper striped wire and tighten.
7. MC wire is the flexible conduit that will keep you from making some of the mistakes from above and it doesn’t cost that much more. Make sure you use the bushings that come with the roll and again watch the termination points for wear. The wire is going to move. For the “non pros” get a mc cutter that will make cutting the cable easy and proper. 12 gauge stranded MC cable will flex enough to make the turns needed and not allow for too sharp of turns.
DC wiring
8. On DC; current and length of the wire run is most important because of the heat gain.
9. Know the total current load of the circuit and go higher wire size.
10. Termination points are most critical on DC because of corrosion. Use a good connecting and an anticorrosion ointment. When designing keep as much of the higher current DC termination points a little more accessible for inspections. Depending on use and load; yearly or couple year inspections.
11. MC Cable also comes in solid wire and would be best used with DC for higher current/power loads.
To summarize just don’t go haphazard into the wiring of the coach. Know what you are going to use the entire circuit for.
Well that’s my rambling on with my 40 plus years as an Electrical/Mechanical Engineer, but what do I know. Bob
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What would cause movement in the wiring?
Wes
Bouncing down the road at 65mph.
Merle.
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I've got romex for all my 110. 10 gauge stranded for DC. I've had no problems. For DC circuits I over compensate for wire gauge.
I've checked temps on wires during highest load and no heat issues. No brownouts at termination points. No cracks or wear.
Some notes if you run wire through conduit-
1. Typical rule of thumb is that the conduit needs to be half empty to allow for airflow and heat dissapation.
2. All wires in the conduit should be able to carry the load of the heaviest wire. So if you have 12 gauge carrying 10amps at 110v don't put it in a conduit with 14 gauge or 16 gauge wire. If the sheathing ever wears or wires break at termination and slide back into the conduit it could be a fire hazard.
Also -
Blue Sea Systems has a phone app called "circuit wizard" which is a great app for determining wire gauge based on loads and length and percentage of time the Max load is on the wire.
Here is a screenshot from the app -
(http://images.tapatalk-cdn.com/15/12/03/5ddf85357fe3ae1b0cb00d99922e5255.jpg)
My biggest electrical issues have been 20 amp 110v from a house plugged into my 20amp to 30amp to 50amp adapters. The adapters don't seem to hold up under a constant 15 amp load.
Also I've seen where the Edison outlet on the house side is 15amp on a 20amp breaker and quickly browns out with a constant load.
Check your adapters! If you have a pin on an adapter that is browned out or plastic melted around it or has black pock marks...get a new one! That's where the fire will start.
-Sean (not Welsh)
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11. MC Cable also comes in solid wire and would be best used with DC for higher current/power loads.
If solid is better why is the best 4/0 DC cable fine strand?
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I'm cornfused...
How is solid better for dc?
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This goes back to the beginning with Nikola Telsa and Thomas Edison. DC current goes one way and sits until needed, When needed it flows fast creating more heat. Solid copper takes the heat better but you need larger wire than you will for AC. It all goes back to the Laws of Thermodynamics. That's what the pointy head engineers say :D
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Bouncing down the road at 65mph.
Merle.
Lol, I was being somewhat of a smart a$$ when I posted that. I honestly don't believe there would be enough movement in the wiring to cause a problem. I do think over loading the wiring or varmits chewing thru the insulation is something to be concerned about, as has been posted. I used bx for my conversion simply because it is metal clad and less likely to be penetrated by a screw or nail.
Wes
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This goes back to the beginning with Nikola Telsa and Thomas Edison. DC current goes one way and sits until needed, When needed it flows fast creating more heat. Solid copper takes the heat better but you need larger wire than you will for AC. It all goes back to the Laws of Thermodynamics. That's what the pointy head engineers say :D
That makes sense now I know why all the big locomotives here use solid wire lol and they vibrate big time
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11. MC Cable also comes in solid wire and would be best used with DC for higher current/power loads.
If solid is better why is the best 4/0 DC cable fine strand?
If 4/0 were coarse-stranded, like THHN, it would be very hard to bend, and if it were solid it would be like a grounding rod! Most readily-available 4/0 is welding cable that needs to be very flexible. It's also much better to crimp lugs on fine-stranded cable than coarser-stranded cable - it's almost impossible to get a good solid gas-tight crimp on coarse-stranded cable with typical consumer-grade crimping tools that can exert only a few tons of force. I tried crimping some lugs onto THHN with both my big FTZ 94284 crimper and my small hydraulic crimper, and neither gave me as good results as with welding cable. Maybe a big industrial crimper would work on coarse-stranded cable, maybe?
This was one reason I used solid metal-jacket 10/3 for my AC wiring - I could form the ends into precise loops that secured very well under the terminal strips' screws inside the junction boxes, much better than trying to crimp lugs onto coarse-stranded MC. I secured this cable every 10 to 12 inches, and it is absolutely immobile.
John
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The question what was best, not what was practical ;D
BX cable is the same as MC but BX has no ground. It uses the metal jacket for the ground. It's also getting hard to find.
Welding cable is SO and is very good but higher priced.
As long as you size the circuit properly and follow good installation practices any wire, even romex is fine.
We all play Russian Rolette with AC power in this application. With no direct ground just one mistake can kill you or burn it down. Under sizing the wire will burn it down, improper termination will burn it down, be it AC or DC, stranded or solid.
If in doubt spend the extra money, use better grade devices, go 1 or2 wire sizes larger, use BC, MC, SO cable for greater protection. Use GFI devices. Fuse/breaker the circuit properly.
Electricity isn't forgiving, doesn't understand, don't allow do overs,,,,,,, it will kill you,,, just be careful, plan, and know what a circuit is doing before running it.
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The bx I use has 3 wires! Also bx is solid wire.
Wes
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Like to hear thoughts on AC/DC bonding and grounding 1 point, 2 points, to bond or not to bond
Do you bond the main panel and have a ground for each AC / DC?
Just curious
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Properly wiring your bus is important if your building, proper maintenance important if store bought, BUT would like to see stats on fires, deaths etc directly related to the wiring in motor homes and buses, not to many I think.
Do it right, doesn't take a rocket scientist to figure it out.
Don't think we need the doom and gloom and talks of death.
Driving your bus across country is far more dangerous imho
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Hi All, I work with television trucks, you may have seen shots of the director looking at a massive wall full of 50 or so television screens connected to cameras out in the field or the arena. These 53ft tractor trailors packed full of every imaginable electronic device, wire, monitor, and electrobic board and computer, these trucks drive mostly on the Interstate, then city streets to get to the showrooms and arenas. These multimillion dollar trucks and trailers, designed by some of the best electronic engineers in the world, have three electronic engineers, that travel with the trucks to each venue, and as we're setting up cameras they are figuring out what broke, came loose, cold solder point broke loose, wire got sliced or crimped and melted, and every imaginable problem causing electronic failure. Mostly because of vibration on the hiway, tom, lvmci...
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You need to those guys to go to air ride trailers Tom ;D
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Hi Clifford, they are air ride and very smooth, it's the twists, turns, pot holes and wear and tear, just like our buses, that cause the wires and connections to break down, tom...
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I must be riding on the smoothest roads in America (NOT, California hwys) we just DO NOT experience the vibrations that you guys are. We have a coffee bar in one of the bay's that when we travel we don't go to any trouble to put cups sugar etc etc away, and we don't have any breakage when we get home. Maybe Prevost rides are better? Maybe I'm just one heck of a driver 👍(probably it).
Back when we had S&S RV's they rattled and vibrated to beat all, and I can't recall one wiring failure. Just saying
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All construction guys have a pile of extention cords somewhere they been meaning to fix or get rid of. Just saying
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Bobwoo,
AC bonding in a conversion is dependent on your set-up. The main concern is if you have a generator or inverter that supplies power to your main panel. Your panel needs a main bonding jumper when you are using either the generator or your inverter. This is the connection between the ground bar and the neutral bar. Your panel should be bonded from the frame to your ground bar at all times. When you are connected to shore power your ground bar and neutral bar should be isolated from one another. Any metal in your conversion needs to be bonded to the ground bar of your electrical panel. As far as DC goes, as long as you have fuses on your circuits and all your metal is bonded together it will take care of any shorts.
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Timely topic - just getting ready to do some rewiring. I was planning on using THHN in blue smurf and non-metalic Liquidtight conduit. BX would be great except most circuits will be a real pain to pull. One issue is concerning me. With some runs having only three conductors, there is plenty of room for them to move/vibrate. What keeps them from chaffing? I was thinking of using expanding nylon sleeveing to bundle them together inside the conduit. With Romex secured every foot movement is virtually non-existant. Especially true if you have multiple runs bundled together. Any thoughts?
I love the new switches and outlets that clamp the conductor and insulation. They are perfect for stranded conductors and eliminate most of the stress on the conductor.
And, speaking of main panel bonding. My conversion panel was incorrectly wired. A standard neutral-ground bond panel was used. Had it been plugged into an incorrectly wired outlet (without GFI) the skin would have been "hot." Don't think that can happen? I found multiple outlets in our rental units which had neutral and hot reversed. Glad I didn't decide to park the bus there and plug it in for some lights! Popping the GFI when plugging into my 50A outlet at home was a clue something was wrong.
NEC Article 551 RV is the bible.
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We have full timed almost 5 years using 12 ga Romex solid core. No issues. FYI, people it doesn't vibrate. Tack it down, make sure your connections are tight and you're good. That being said, it was a major pain to get wired and into light switch boxes etc. greatest fire risk for me is wire nuts jammed into small boxes and loosish connections as a result.
Sent from my iPhone using Tapatalk
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Instead of wire nuts , you could crimp and solder the wires together using copper tubing. Then insulate then with the real heavy duty black tape. The rubbery kind not the vinyl stuff. It would take a while longer but would last forever. Probably would help to roughen the wire a little before soldering and by a real good crimping tool.
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That would actually be a much cleaner way. I should experiment with that method
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It is a lot easier to use the crimp snap type you crimp the connector (copper) and the cap snap on then it looks like a wing nut easy to fit in a box and the connection is permanent or use what is called the closed end crimp connector JMO I don't care for wire nuts and tape
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soldering (properly) is not as easy as some would have you believe ....
and the consequences equally disturbing. if it was simple, crimping would not be an option...
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I have used both the closed end connectors and Buchannan crimp connectors for years. Used with the appropiate crimper specified by the manufacturer they are excellent. They are especially well suited for stranded wire.
Think I'm going to go the Romex route for interior runs. If this were a new conversion with open walls, conduit would be my choice. Liquidtight conduit will still be used for under the floor, weather exposed locations.
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They crimp and solder most gang connections on cars and trucks and put a few layers of cloth tape on them all the time using narrow copper crimps. Now they fuse the connections with some kind of sonic pressure welder and wrap in heat shrink with glue. I also wanted to add that split loom is pretty nice and a lot easier to install than conduit. They have been using it in cars for 20 plus years and works the same as conduit. I need to run a new circuit and it would be easier if it was split loom not conduit. I think as long as you don't let the solid wire flex it won't break. I don't think the copper wire today is as brittle as before, I'm pretty sure it's an alloy type copper now. Besides the fact that if your bus was flexing the wiring enough to break it, my guess is the wire is not the only thing that is broken.
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Bobwoo,
AC bonding in a conversion is dependent on your set-up. The main concern is if you have a generator or inverter that supplies power to your main panel. Your panel needs a main bonding jumper when you are using either the generator or your inverter. This is the connection between the ground bar and the neutral bar. Your panel should be bonded from the frame to your ground bar at all times. When you are connected to shore power your ground bar and neutral bar should be isolated from one another. Any metal in your conversion needs to be bonded to the ground bar of your electrical panel. As far as DC goes, as long as you have fuses on your circuits and all your metal is bonded together it will take care of any shorts.
Im assumin you are talking about bonding your ground and neutral. You have to be very careful with this.
I belive the proper practice is that It should be bonded at the generator or inverter. Most Marine/RV generators or inverters allow for this.
The problem arises when you go to hook up your bus to an RV park pedastal. Because the ground/neutral is bonded on the parks source side it creates a situation where the bonded neutral and ground in your panel creates a ground that is now hot!
It can be dangerous for you and whoever needs to work on the electrical from the other end. It can also create a "hot skin" condition where the metal on your rig is now hot and you can get electrocuted by touching it.
Best practice is to bond ground and neutral at the source (generator or inverter) not at the panel.
-Sean
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Sean, yes that is a part of what I was talking about.
Yes you do want to bond at the generator and inverter, but you need to make sure that you have some way of disconnecting from from the bonded point when you are connected to the park source. Some folks keep it simple by just using their shore power cord and plugging it in to the generator or the park pedestal. You can also use a automatic transfer switch, but you will need to make sure that you are switching the 2 hots and the neutral. This will disconnect you from the neutral to ground bond at the generator when you are using the park source. It will be the same situation for your inverter.
It is equally important that your panel ground is attached to the bus frame and or any metal parts in the bus. This ensures that the over current protection (breakers) will work in the event that a hot wire touches any of the metal parts of your bus. This will also eliminate the possibility of the skin being hot.
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Tom LVMCI, so now I have to hire an electronic engineer to ride along with us. What next? and will he fit in a bay for storage? ::)
We have Romex for AC and DC is stranded 12. I still have more to redo from PO who would just cut it wherever and take off. I had 1 i found on the DC side and it was 4 feet long with 16 connections and different colors?????? :o
Dave5Cs
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Hi Dave, Sean will tell you about how different video engineers are, it would be better to buy him a 24 pack of beer and ask him to fix it before you leave, tom...
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Hi Dave, Sean will tell you about how different video engineers are, it would be better to buy him a 24 pack of beer and ask him to fix it before you leave, tom...
Video Engineers? Don't get me started :)
How about the video guy calling cameras cause the camera caller didn't show up. Hahaha...
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All construction guys have a pile of extention cords somewhere they been meaning to fix or get rid of. Just saying
And a lot of those are because the cords got stretched. They rely on the strands of conductors for their strength and their own weight will stretch them (making the individual strands thinner and less able to carry current) if they're left hanging or if they're stressed, like if someone trips over them and pulls them. A couple of strands are so thin they overheat and melt, then all the current is put through the remaining strands and that overloads them. Extension cords are good for what they are, but you have to be careful about how they're used and treated.
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And a lot of those are because the cords got stretched. They rely on the strands of conductors for their strength and their own weight will stretch them (making the individual strands thinner and less able to carry current) if they're left hanging or if they're stressed, like if someone trips over them and pulls them. A couple of strands are so thin they overheat and melt, then all the current is put through the remaining strands and that overloads them. Extension cords are good for what they are, but you have to be careful about how they're used and treated.
They have a pile because of OHSA I can't began to tell you how many rounds I went with OHSA because of extension cords and ladders.LOL we would sell off the ladders and cords every year and it almost payed for the employees Christmas party
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Every portable gravel crusher in America runs on SO cord.
There is not a harsher vibrating shaking dirtier place to conduct electricity (and lots of it)....never replaced a wire...
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Clifford don't forget Chopping cord ends off because the Ground was the wrong way for the new codes & Hard hats that were out of date.... Fall devices that had never been used but the date was more than a year old.Scaffold nets..... Don't get me started!, Oh you already did!... ;D
Dave
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Yes and don't ever tell one "write the damn citation" BTDT ;D